You could just refuse to talk at the doors due to anxiety. No one wants to work with ones too anxious to do their half of the doors. If you do find someone happy to have you walk with them while they do the doors you can just see it as getting exercise.
After a while you can refuse to go altogether because you don't feel it right to count time witnessing when you actually don't witness and you still can't do it due to anxiety.
You can then say you will stick to informal witnessing. Done.